Method for processing an ultrasonic analog signal, digital signal processing unit and ultrasonic inspection device

Abstract

The invention relates to a method for processing an ultrasonic analog signal (10) representing a reflected ultrasonic wave, wherein the ultrasonic analog signal (10) is fed in a parallel manner into at least two signal paths (A;B) and the ultrasonic analog signal is supplied in each signal path (A;B) to respective amplifiers (20A;20B) whose gains are different from one another. The ultrasonic analog signals (11;11′) which have thus been amplified differently are supplied in each signal path (A;B) to a respective A / D converter (30A;30B) which converts the amplified ultrasonic analog signals (11; 11′) into digital ultrasonic data (12;12′), from which a combined digital ultrasonic signal (15) is reconstructed after further processing steps. According to the invention, a decomposition of the digital ultrasonic data (12; 12′) is carried out in each signal path (A;B) by the first level of a wavelet filter algorithm, and the wavelet coefficients are altered by a threshold analysis. A combined digital ultrasonic signal (15) is then reconstructed from the ultrasonic data thus decomposed, wherein an inverse transformation of the combined ultrasonic signal (15) is carried out by the second level of the wavelet filter algorithm with the altered wavelet coefficients. The invention moreover relates to an associated signal processing unit and an ultrasonic inspection device comprising such a signal processing unit.

Description

FIELD OF THE INVENTION[0001]Embodiments of the present invention relate to a method for processing an ultrasonic analog signal representing an ultrasonic wave reflected in an inspected object.[0002]Embodiments of the present invention also relate to an associated signal processing unit and an ultrasonic inspection device using such a signal processing unit.BACKGROUND OF THE INVENTION[0003]A variety of methods for the non-destructive inspection of a test object by means of ultrasound are known from the field of material testing. In the pulse echo methods, a short ultrasonic pulse generated by an ultrasonic transmitter (transducer) is suitably insonified into a test object so that it propagates in the test object. If the pulse hits a flaw in the test object, for example a discontinuity, the pulse is reflected at least partially. The reflected pulse is detected by means of an ultrasonic receiver. The position of the discontinuity in the test object can be deduced from the travel time b...

AI Technical Summary

Benefits of technology

The present invention provides a signal processing unit for ultrasonic inspection devices that uses a wavelet filter algorithm to decomposing and altering the digital ultrasonic data. The unit has two embodiments: the first embodiment uses a single level of wavelet filter algorithm, while the second embodiment uses a combined approach of decomposing the data and altering the wavelet coefficients. The second embodiment also allows for separate inverse transformation of the decomposed ultrasonic data with the altered wavelet coefficients. This results in a combined ultrasonic signal with a high dynamic range. The invention also allows for flexibility in adjusting the threshold values for defect detection, which can capture defects close to the surface of the inspected object. Overall, the invention improves the accuracy and reliability of ultrasonic inspection devices.

Problems solved by technology

Even though the pulse echo methods have been established methods in the field of material testing for many years, their application was generally limited to such inspection cases in which flaws are to be detected in the full test object volume.

However, if flaws occur in the vicinity of such structures of the test object which themselves reflect the ultrasonic pulses used for the inspection, the detection of such flaws in the test object is difficult.

In such a case, the pulse reflected at the flaw overlaps with the pulse reflected at the reflecting structure of the test object, so that a reliable detection of the flaw is often problematic or even impossible.

However, possible geometry echoes can lead to a relatively weak signal of a flaw being incapable of being displayed if it is superimposed by other signals.

Large amplitude differences of several received signals thus render smaller signals difficult to detect.

However, these components and circuits may in turn involve new problems with regard to the calibration and with respect to the reliability and consistency of the results, which have to be resolved.

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